Davies has made documentaries for ITV's World in Action and written numerous books on the subject of politics and journalism, including Flat Earth News, which attracted considerable controversy as an exposé of journalistic malpractice in the UK and around the globe.[3] As a reporter for The Guardian, Davies was responsible for uncovering the News of the World phone hacking affair, including the July 2011 revelations of hacking into the mobile phone voicemail of the murdered schoolgirl Milly Dowler.

Flat Earth News was greeted in the London Review of Books on its publication as "a genuinely important book, one which is likely to change, permanently, the way anyone who reads it looks at the British newspaper industry".[12] The LRB highlighted the analysis showing that 60% of the content of UK papers was based mainly on wire copy or press releases, while only 12% are original stories and only 12% of stories showed evidence that the central statement had been corroborated (seeChurnalism). Mary Riddell in The Observer disputed some of the charges against British journalism in the book, and described it as "unduly pessimistic".[13]Peter Oborne in The Spectator concentrated on the use of illegal techniques to invade privacy rather than declining standards, describing Flat Earth News as "hypnotically readable" and praising the collection of evidence that the practice of journalism is "bent", although qualifying this somewhat by suggesting that Davies "ignores a great deal [of journalism] that is salient and good".[14]